The present disclosure involves a centrifugal pump 100. The mechanism of a centrifugal pump 100 is well known to those skilled in the art. The centrifugal pump 100 is connected to a source of fluid to be transported. A rotating shaft 102 rotates an impeller 306 creating a negative pressure to pull the fluid into the centrifugal pump 100 to be discharged.
The outer portion of the centrifugal pump 100 is formed by centrifugal pump housing 302 coupled to a stuffing box 202 that seals the rear of the centrifugal pump 100. The stuffing box 202 contains a stuffing box throat 204 with a stuffing box throat aperture 210 that allows the rotating shaft 102 to be inserted into the stuffing box 202 to connect with the impeller 306. Due to the pressure of fluid within the centrifugal pump 100, there is a potential for leakage from the stuffing box 202 where the rotating shaft 102 enters the stuffing box throat aperture 210. The space between the rotating shaft 102 and the stuffing box throat aperture 210 is filled with a seal that typically encircles the rotating shaft 102 near the distal end of the stuffing box throat 204.
Seals used in a centrifugal pump 100 may take many forms. One example is compression packing, also known as rope packing. Compression packing encircles the rotating shaft 102 is such a manner that when the stuffing box 202 is installed on the centrifugal pump 100, the compression packing is within the stuffing box throat 204. A gland coupled to the stuffing box 202 exerts pressure into the stuffing box 202 and the compression packing to keep the compression packing in position. The displacement of the compression packing by the gland acts as a seal.
In order for the compression packing to maintain integrity and act as a seal, it needs to remain lubricated. In oil field embodiments, the centrifugal pump 100 uses the fluid being transported as a lubricant for seals. If for some reason the centrifugal pump 100 runs during an interruption in the fluid flow, then the centrifugal pump 100 will operate without the benefit of lubrication. This will increase friction on the rotating shaft 102, which will cause an increase in temperature that will ruin the seals. A ruined seal will force the operators to repair the pump or replace the centrifugal pump 100 and send the damaged centrifugal pump 100 for service. Additionally, even with proper lubrication, seals in a centrifugal pump 100 leak lubricant.
Pump seals can fail for other reasons. Besides the interruption of fluid during operations, a centrifugal pump 100 may be started with insufficient prime. If there is no prime, then the fluid will not reach the seals to lubricate them. Once the centrifugal pump 100 starts operations, the movement of the rotating shaft 102 without adequate lubrication will cause friction, leading to heat buildup, compromising the seals. These and other previously unrecognized problems in the background of the invention lead to further development of the invention.